Various materials have been utilized in the past for coating and insulating electrical conductors. Among the more commonly used coatings are the conventional enamel or resinous varnish-type coatings, polyvinyl resins, polystyrene resins, etc. All these coating compositions, while providing insulation, have been found to be lacking in one respect or another or to inherently involve certain disadvantages. For example, the enamel or varnish coatings lack adequate flexibility. Rubber coatings such as polybutadiene, ethylene-propylene rubbers, and natural rubber require vulcanization in order to obtain their maximum desired set of physical properties. Furthermore, most rubber coatings deteriorate with age and exposure to the atmosphere, resulting in the cracking and peeling of the rubber coatings. The polyvinyl and polystyrene resin coatings must be plasticized in order to have sufficient flexibility. Such coatings often lose plasticizers during aging and then become brittle.
Recent improvements in the art of polymerization have enabled the production of certain block copolymers which have been found to be eminately suitable for electrical conductor coatings in view of their unexpectedly superior set of electrical properties combined with their superior physical properties. However, these coatings, such as the coatings disclosed in U.S. Pat. No. 3,639,163, lack sufficient fire resistance to be useful in many desirable applications.